A Post represents a content object, pulled in from social media providers from a Source. It's the primary source of content, and what you'll want to actually show on your site.
You'll need to either fetch posts from a Feed or a Source.
{# Get the source by its handle #}
{% set source = craft.socialFeeds.getSourceByHandle('mySourceHandle') %}
{% set posts = source.getPosts() %}
{# OR get the Posts from a Feed (multiple Sources) #}
{% set posts = craft.socialFeeds.getPosts('myFeedHandle') %}
{% for post in posts %}
ID: {{ post.id }}<br>
Content: {{ post.getContent() }}
{% endfor %}
Check out our guide on Rendering Posts for more.